This invention relates to apparatus for transferring articles such as absorbent pads in the manufacture of disposable absorbent articles such as diapers, incontinence control garments or female sanitary pads as they advance along a production line.
In the production and manufacture of disposable products such as sanitary napkins or pants-type diapers, it frequently becomes necessary to manufacture a component of the product in one orientation, and then to rotate that component part 90xc2x0 so that it is suitably oriented for use in another step in the production process. Various devices have been developed for this purpose and are known to those experienced in the industry. Examples of such apparatus are those described in U.S. Pat. Nos. 4,726,876, 4,880,102 and 5,025,910.
One common method for reorienting such product parts, such as absorbent pads, is to transfer them to a large rotating device, where each part is retained by vacuum on an individual head. The heads each successively pick up one of the parts, are caused to rotate 90xc2x0 by means of cams or gears, and then caused to deposit the part, after 90xc2x0 reorientation, onto the next downstream conveyor.
In most applications of this type, the amount of convexity of the vacuum head (i.e., the arc segment angle) is kept to a minimum so as to create the least amount of chord height. This becomes less practical as product length increases, as the required diameter of the turning drum becomes unreasonably large. As the chord height becomes larger, the machine designer must find a compromise between the need for maintaining control of the ends of the product and the need for achieving a firm placement of the product""s center section.
Additionally, the product being transferred may possess certain contractile forces which tend to cause unwanted retraction of the ends of the pads during the transfer process.
It is an object of this invention to solve the aforementioned problems typically associated with transfer devices. In accord with an important aspect of the invention, the product is picked up from a toroidal or convex surface and placed on a flat surface while being, in the process, stretched to a fully extended condition. Additionally, it is an object of this invention to provide these capabilities with apparatus requiring a minimum of moving parts. The apparatus of this invention is of particular benefit where an article to be transferred is subject to internally biasing elastic forces, for example, various types of disposable diapers and, especially, absorbent pads used in the manufacture of such diapers, which pads may contain elastic materials.
The invention includes a coordinated set of three aligned vacuum wheels, which pick the products up from the surface of an upstream product turner or conveyor and place the product onto a destination conveyor later in their rotation. The two outermost wheels (outboard wheels) are truncated cones, with their inboard diameters smaller than their outboard diameters. The center, or inboard wheel is cylindrical in shape. In a preferred embodiment, each wheel is provided with a vacuum pattern arranged to positively attract and hold the individual products.
The outboard wheels are canted with respect to the central wheel so that their faces are approximately parallel to the product surfaces at the point of acquisition or picking up of the product. This angle of cant also places the faces of the outboard wheels, when viewed at the deposition point, in a aligned straight line, parallel to and generally in the same tangental plane as the center wheel. At this point, approximately 180xc2x0 from the acquisition point, the product is deposited onto a traveling destination conveyor where it may be secured by mechanical means, vacuum or adhesive.
As the outboard canted wheels or drums rotate, their vacuum faces move away from the product centerline. This effect serves to stretch the product and pull it to its fully extended length. Inasmuch as the amount of extension of the wheels may exceed the actual maximum length of the product, the intention is that the ends of the product are able to slip across the face of the canted wheels in the event that the extension tensile force exceeds the force required to overcome the effects of friction. As a means of preventing the body of the transferred product from being pulled off of the centerline, the surface materials selected for the center wheel or drum preferably have a higher coefficient of friction with the product than do the surfaces of the canted outboard drums. Alternatively, a higher vacuum level or a more advantageous pattern of vacuum holes may serve to hold the product more securely to the center wheel.